1. Field of the Invention
The invention relates to a non-influencing fastener, and specifically to a non-influencing fastener for mounting a heat sink in contact with an electronic component.
2. Background Information
Electronic components, such as microprocessors and integrated circuits, must operate within certain specified temperature ranges to perform properly. Excessive heat degrades electronic component performance, reliability, life expectancy, and can even cause failure. Heat sinks are widely used for dissipating excessive heat. Typically, heat sinks are formed with fins, pins or other similar structures to increase the surface area of the heat sink and thereby enhance heat dissipation as air passes over the heat sink. Where large amounts of heat are to be dissipated, heat sinks may contain high performance structures, such as vapor chambers and/or heat pipes, to further enhance heat transfer. Heat sinks are typically formed of metals, such as copper or aluminum. More recently, graphite-based materials have been used for heat sinks because such materials offer several advantages, such as improved thermal conductivity and reduced weight.
Electronic components are generally packaged using electronic packages (i.e., modules) that include a module substrate to which the electronic component is electronically connected. In some cases, the module includes a cap (i.e., a capped module) which seals the electronic component within the module. In other cases, the module does not include a cap (i.e., a bare die module). Bare die modules typically exhibit better thermal performance than capped modules because bare die modules eliminate two sources of thermal resistance present in capped modules, i.e., the thermal resistance of the cap and the thermal resistance of the thermal interface between the cap and the electronic component. For small heatsinks, the thermal interface material can be an adhesive and the bare die module is capable of carrying the mass of the heatsink during any shock or vibration event. However, as component power dissipation increases, the volume and mass of the heatsink increase accordingly, and the bare die can no longer support the mass of the heatsink alone.
Larger heat sinks can be attached to modules using a variety of attachment mechanisms, such as clamps, screws, and other hardware. The attachment mechanism typically applies a force that maintains a thermal interface gap, i.e., the thickness of the thermal interface between the heat sink and the module. If a capped module is used in such applications, the cap protects the electronic component from physical damage from the applied force. However, as noted, bare die modules have better thermal transfer performance than capped modules. If a bare die module is used, the applied force is transferred directly through the electronic component itself. Consequently, when bare die modules are used, care must be taken to apply only a controlled amount of force and the attachment mechanism for the heat sink requires a non-influencing fastener, i.e., one that locks in the position of the heat sink without influencing the force applied to the thermal interface gap.